Evaporative pattern casting is a type of casting method, and is also called full-mold casting. An outline of this method is as follows. First, a pattern is made from an evaporative material that evaporates by the heat of molten metal. This pattern is called an evaporative pattern. Next, a sand mold is made in which the evaporative pattern is embedded. Molten metal is poured into a cavity of the sand mold. Here, “cavity” means a space in the sand mold occupied by the evaporative pattern. When the molten metal is poured, the evaporative pattern is evaporated (melted or burnt) by the heat of the molten metal, and the space which had been occupied by the evaporative pattern is filled by the molten metal. After the molten metal has cooled and solidified, the sand mold is removed, completing a cast structure having exactly the same shape as the evaporative pattern. Typically, polystyrene foam or wax is employed as the evaporative material.
The structural strength (rigidity) of polystyrene foam or wax is low, and consequently when a large-scale evaporative pattern was to be made, the evaporative pattern was manufactured as a plurality of separate parts, and then the parts were assembled. For example, a method of manufacturing an evaporative pattern as a plurality of separate parts is disclosed in Patent Document 1.